I am facing a strange problem with the search engine of my WordPress website.

I want to turn off the case sensitivity of my WordPress search engine.

For example if a user search “apple of one’s eye” it returns no results. See here.

And user leaves the sites thinking it’s not available, whereas the same post is available with a bit different title or content.

And if a user search “apple eye” then there is more than one post available. theidioms.com/?s=apple+eye

Now I just want to narrow user’s search and ignore some specific words like “of”, “one’s”, “the”, “on” and so on.

How is it possible?
How to Ignore Specific/Common Words and Special Characters in WordPress Search Query?

Please help!